1. Field of the Invention
The present invention concerns those fields involving the manufacture of electronic components, primarily the fabrication of integrated circuits from substrates or semiconductor wafer materials, such as silicon, more particularly the mechanical procedures and devices used to change the position of at least one semiconductor wafer provided with at least one positioning mark and placed in a support intended to hold a plurality of semiconductor wafers.
2. Discussion of Related Art
The prior art teaches that such methods consist primarily in grasping a semiconductor wafer by one of its faces to change its position, primarily by displacing it from one location to another, whereby devices used to implement these methods comprise means allowing a wafer to be grasped by suction in the central region of one of its faces. Independently of the displacement of the wafers from one location to another, the semiconductor wafers are oriented in such a way that their positioning mark is placed in a predetermined position, which operation may consist, for example, in aligning the positioning marks on all the wafers intended to be moved or situated in a common support.
The disadvantage of the methods and devices of the prior art is that they can lead to contamination of the semiconductor wafers resulting from the grasping of said wafers by one of their faces, which consists of a material that is highly sensitive to various forms of contamination, the risk of contamination being further enhanced by the fact that there is contact between the face and an object. Moreover, the methods and devices according to the prior art require considerable time for the operations of displacement and orientation of one or several semiconductor wafers, these operations being managed independently, which results in longer processing periods for semiconductor wafers and therefore higher processing costs.
We are familiar with document U.S. Pat. No. 5,102,291, which refers to a method and apparatus for orienting a silicon wafer located in a support by grasping its periphery so as to minimize possible contamination from direct contact with its faces. Wafers are grasped one by one between two gripper arms movable in translation with respect to one another along a straight line, which are urged toward each other in translation along the guide direction until the two arms exert pressure against the periphery of the wafer being grasped by means of four pressure wheels that lift the wafer prior to contact of the wheels against the periphery of the wafer, the grasped silicon wafer being capable of being rotationally oriented to a specific position with respect to the support by means of pressure wheels rotating in the plane of the wafer, at least one of which is motorized. Moreover, the apparatus is used to move the grasped wafer in a straight line only because of the two gripper arms. Detection of the desired orientation of the wafer can take place by means of a mechanical, optical, electrical, or other type of sensor. For wafers provided with a notch, the document specifies a pin that is smaller than the notch and which penetrates the notch when the wafer is in a desired position.
We are also familiar with U.S. Pat. No. 5,445,486, which relates to an apparatus for transferring silicon wafers from one support to another by means of a gripper arm inserted between wafers in a support, the gripper arm grasping one or more wafers by the periphery of their bottom surface. The apparatus does not have a means for orienting the transferred wafers.
The intended processing of semiconductor wafers can include any process involving a change in position of a wafer, of several wafers, or of all the semiconductor wafers located in a common support, as, for example, the transfer of wafers from one support to another, the alignment of marks for the purpose of identifying wafers in the support, or even modification of the angular position of the semiconductor wafer found in the support for the placement of marks at a predetermined position.
The present invention proposes to overcome the above disadvantages and provide other advantages. One object of the present invention is to enable the change of position of at least one semiconductor wafer while avoiding any contamination resulting from grasping the wafer by one of its faces and, furthermore, reducing the risks of contamination.
Another object of the present invention is to enable a change of position of at least one semiconductor wafer, thus modifying the orientation of a wafer while another processing operation is taking place, especially the displacement or transfer of the wafer.
Another object of the present invention is to provide increased space within a semiconductor wafer processing station by eliminating the need for specific equipment for the orientation or alignment of positioning marks on wafers.
Another object of the present invention is to enable a plurality of semiconductor wafers to be grasped and oriented, the orientation of the wafers occurring simultaneously and, moreover, simultaneously with another operation, such as the displacement of a plurality of wafers.
More specifically the invention consists in a mechanical method for changing the position of at least one semiconductor wafer provided with at least one positioning mark and placed in a support intended to house a plurality of semiconductor wafers, characterized in that it comprises the following steps:
penetration of said support by means of a gripper arm with a first movement of said arm according to a first direction in space
seizure of said at least one semiconductor wafer by the periphery of said wafer with a second movement of said arm according to a second direction in space
orientation of said at least one semiconductor wafer, grasped in such a way that said positioning mark is placed in a predetermined position.
Seizure of the semiconductor wafer by its periphery helps reduce contamination of the wafer and helps avoid contamination resulting from grasping a face of the semiconductor wafer, while orientation of the wafer when grasped enables this operation to take place simultaneously with other operations, such as displacement of the wafer. The operation of orienting a wafer when it is being seized helps avoid the use of a specific processing station for orienting the semiconductor wafers, resulting in increased space for processing the wafers.
According to an advantageous characteristic of the invention, the method according to the invention also comprises the following steps:
withdrawal of said at least one semiconductor wafer from said support with a third movement of said gripper arm along said first direction, opposite said first movement
displacement of said at least one semiconductor wafer from one location to another in a three-directional or -dimensional space, with movements of said arm being chosen from among the three directions in space, said step consisting of
orienting said at least one semiconductor wafer in such a way as to place said positioning mark in a predetermined position, simultaneously with movements of said gripper arm.
According to an advantageous characteristic, the method according to the invention consists in:
penetration by means of a gripper arm of said support with a first movement of said arm along a first direction in space
seizure of a plurality of semiconductor wafers by their periphery with a second movement of said arm along a second direction in space
orientation of said semiconductor wafers in such a way as to align said respective positioning marks of said semiconductor wafers.
According to an advantageous characteristic, the above method also comprises the following steps:
withdrawal of said plurality of semiconductor wafers from said support with a third displacement of said gripper arm along said first direction, opposite said first displacement
displacement of said plurality of semiconductor wafers from one location to another in a three-directional or -dimensional space, with displacements of said arm chosen from among the three directions of space, said step consisting in the orientation of said grasped semiconductor wafers in such a way as to align their respective positioning marks and taking place simultaneously with displacements of said gripper arm.
The invention also concerns a device for changing the position of at least one semiconductor wafer provided with at least one positioning mark and placed in a support intended to house a plurality of semiconductor wafers, said device comprising a gripper arm of said at least one semiconductor wafer, means for displacing said gripper arm, said gripper arm comprising:
means for gripping said at least one semiconductor wafer by its periphery
means for orienting said at least one semiconductor wafer, said orienting means cooperating with said grasping means to place said positioning mark in a predetermined position said grasping means and said orientation means being arranged on a rigid structure, said grasping means being distributed along the perimeter of the periphery of said at least one semiconductor wafer, and in that said displacement means of said gripper arm comprises means for displacement along three directions in space.
According to an advantageous characteristic, said gripping means comprise:
means for grasping the periphery of a plurality of semiconductor wafers
means for orienting said semiconductor wafers, said orienting means cooperating with said means of grasping so as to align said respective positioning marks of said semiconductor wafers.
The invention also concerns a semiconductor wafer gripper arm provided with at least one positioning mark, to realize the seizure of at least one semiconductor wafer placed in a support intended to house a plurality of semiconductor wafers, characterized in that said arm comprises:
means for grasping the periphery of said at least one semiconductor wafer
means for orienting said at least one semiconductor wafer, said orienting means cooperating with said grasping means so as to place said positioning mark in a predetermined position
said grasping means and said orientation means being arranged on a rigid structure, said grasping means being distributed over the perimeter of the periphery of said at least one semiconductor wafer.
According to an advantageous characteristic, said grasping means comprise at least three stops provided respectively with a degree of freedom in rotation and distributed along the perimeter of the periphery of said at least one semiconductor wafer, and said means of orientation comprise a friction-operated drive roller for said at least one semiconductor wafer.
According to another advantageous characteristic, said drive roller consists of one of said three stops that is at least partially a driving element.
According to another advantageous characteristic, said positioning mark is a notch placed along the periphery of said at least one semiconductor wafer, and said three stops comprise respectively two freely rotating adjacent driven rollers.
According to another advantageous characteristic, said driven rollers have respectively at least one first frustoconical contact surface to provide support for said at least one semiconductor wafer by means of a peripheral edge on said wafer.
According to another advantageous characteristic, a generatrix of said at least first frustoconical contact surface forms an angle of between 5xc2x0 and 45xc2x0 with a perpendicular to said at least one semiconductor wafer.
According to another advantageous characteristic, said driven rollers have, respectively, a second frustoconical surface whose apex is connected to the base of said first frustoconical surface and whose generatrix forms an angle with a perpendicular to said at least one semiconductor wafer, greater than the angle of the generatrix of said first frustoconical surface.
According to another advantageous characteristic, said means of orientation comprise a first beam capable of being cut whenever said notch is not opposite said first beam, and a detector for detecting when said first beam has been cut.
ding to another advantageous characteristic, the gripper arm according to the invention comprises means for locating the position of said at least one semiconductor wafer when it is placed in said support.
According to another advantageous characteristic, said locator means comprise a second beam cooperating with said first beam and a dimension characteristic of said at least one semiconductor wafer to assist in establishing the position of said at least one semiconductor wafer in said support.
According to another advantageous characteristic, said locator means comprise a third beam cooperating with said first or second beams and a dimension characteristic of said at least one semiconductor wafer to assist in establishing the position of said at least one semiconductor wafer in said support when said first or second beam is placed opposite said notch.
According to another advantageous characteristic, the gripper arm according to the invention comprises:
means for grasping a plurality of semiconductor wafers by the periphery
means for orienting said grasped semiconductor wafers, said orienting means cooperating with said grasping means to align said respective positioning marks of said semiconductor wafers.